Stent

ABSTRACT

A stent with strut bands and connectors, wherein the strut bands have long and short struts with a junction positioned between the short struts. Each junction defines a reservoir, wherein the reservoirs of a strut band are substantially circumferentially aligned. The connectors each have arms, wherein each arm includes an opposing U-shaped link. The opposing links have a shared portion disposed between a peak on one strut band and a longitudinally adjacent trough of an adjacent strut band.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional application from Ser. No. 11/960,333,filed Dec. 19, 2007, the contents of which is hereby incorporated byreference

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable

FIELD OF THE INVENTION

This invention relates to an endoprosthesis device for implantationwithin a body vessel, typically a blood vessel. More specifically, itrelates to a tubular expandable stent having improved structural aspectsas well as improved drug retention/delivery capabilities.

BACKGROUND OF THE INVENTION

Stents, grafts, stent-grafts, vena cava filters, expandable frameworks,and similar implantable medical devices, collectively referred tohereinafter as stents, are radially expandable endoprostheses which aretypically intravascular implants capable of being implantedtransluminally and enlarged radially after being introducedpercutaneously. Stents may be implanted in a variety of body lumens orvessels such as within the vascular system, urinary tracts, bile ducts,fallopian tubes, coronary vessels, secondary vessels, etc. Stents may beused to support body vessels and to prevent restenosis followingangioplasty in the vascular system. They may be self-expanding, expandedby an internal radial force, such as when mounted on a balloon, or acombination of self-expanding and balloon expandable (hybridexpandable).

Stents may be created by methods including cutting or etching a designfrom a tubular stock, from a flat sheet which is cut or etched and whichis subsequently rolled, and/or from one or more interwoven wires orbraids.

Known construction materials for use in stents include polymers, organicfabrics, and biocompatible metals. Metals and/or alloys of such metalsthat have been used in the construction of stents and/or theircomponents include but are not limited to: stainless steel, gold,silver, tantalum, titanium, chromium, cobalt and shape memory alloyssuch as Nitinol.

In an effort to combat vessel restenosis, as well as other medicalconditions, stents have been employed to delivery a variety oftherapeutic agents directly to the site of stent deployment. Some stentsemploy a variety of structural features, such as slots, grooves, holes,chambers, etc, to act as reservoirs for a therapeutic agent and/or othersubstances.

There remains a need for drug delivery stents that have improvedstructural performance characteristics, such as improved flexibility,structural integrity, compression resistance, etc. There also remains aneed to provide such stents with a more desirable drug delivery profile.

The art referred to and/or described above is not intended to constitutean admission that any patent, publication or other information referredto herein is “prior art” with respect to this invention. In addition,this section should not be construed to mean that a search has been madeor that no other pertinent information as defined in 37 C.F.R. §1.56(a)exists.

All US patents and applications and all other published documentsmentioned anywhere in this application are incorporated herein byreference in their entirety.

Without limiting the scope of the invention a brief summary of some ofthe claimed embodiments of the invention is set forth below. Additionaldetails of the summarized embodiments of the invention and/or additionalembodiments of the invention may be found in the Detailed Description ofthe Invention below.

A brief abstract of the technical disclosure in the specification isprovided as well only for the purposes of complying with 37 C.F.R. 1.72.The abstract is not intended to be used for interpreting the scope ofthe claims.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to stent structures,which when used for the delivery of therapeutic agents such as drugs,provide improved drug delivery characteristics. The unique arrangementand configuration of drug delivery reservoirs throughout the stentstructure provide improved drug delivery characteristics withoutcompromise to the stent's performance characteristics.

Embodiments of the present invention include stents, which have improvedflexibility, but also sufficient structural strength to permit thestents to traverse the tortuous confines of mammalian anatomy. In someembodiments the stent of the present invention are provided with strutbands of long and short struts, wherein pairs of short struts areconnected to one another at junctions. The junctions provide acircumferential offset within the strut band.

In some embodiments the stents are provided with connectors between thestrut bands, which have opposingly oriented U-shaped links, wherein eachlink extends from a junction of adjacent strut bands.

The combination of the structural features provided in the stents of thepresent invention provide a structurally improved, highly flexiblestent.

An additional goal of the present invention however, is to providestents with improved drug delivery characteristics as well. This goal isachieved by providing stents with drug delivery reservoirs that arepositioned in and defined by the strut band junctions, as well as theconnectors, and in some cases the struts as well. In some embodiments atleast some of the reservoirs are provided in circumferentially alignedcolumns about the stent.

Reservoirs can be any type of surface feature suitable for containing adefined amount of therapeutic agent(s) such as a drug or drug/polymermatrix. In some embodiments one or more of the reservoirs extend onlypartially through the thickness of the stent with only a single openingon either the inner surface (luminal) or outer surface (abluminal) ofthe stent. In some embodiments, one or more of the reservoirs is athrough-hole which extends entirely through the thickness of the stentbody. Each reservoir can have a constant or varied cross-sectional areathroughout its thicknesses. Each reservoir opening can have any of avariety of sizes or shapes.

These and other embodiments which characterize the invention are pointedout with particularity in the claims annexed hereto and forming a parthereof. However, for further understanding of the invention, itsadvantages and objectives obtained by its use, reference can be made tothe drawings which form a further part hereof and the accompanyingdescriptive matter, in which there is illustrated and described aembodiments of the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

A detailed description of the invention is hereafter described withspecific reference being made to the drawings.

FIG. 1 shows a flat pattern view of an embodiment of the invention.

FIG. 2 shows a flat pattern view of an embodiment of the invention.

FIG. 3 shows a flat pattern view of an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many different forms, there aredescribed in detail herein specific embodiments of the invention. Thisdescription is an exemplification of the principles of the invention andis not intended to limit the invention to the particular embodimentsillustrated.

For the purposes of this disclosure, like reference numerals in thefigures shall refer to like features unless otherwise indicated.

At least one embodiment of the present invention is directed to a stent10, an example of which is illustrated in FIG. 1. The structure of stent10 is comprised of a plurality of strut bands 20 and connectors 40.

Each strut band 20 forms a closed path of alternating peaks 22 andtroughs 24. Strut bands 20 that are adjacent one another are connectedby at least one connector 40.

Each strut band 20 comprises a plurality of long struts 30, a pluralityof first short struts 32 and second short struts 34, and a plurality ofjunctions 36. Each junction 36 is positioned between and connects afirst short strut 32 and a second short strut 34. In the embodimentsdepicted in FIGS. 1-3, within each strut band 20 each first short strut32 is longitudinally and circumferentially offset from each second shortstrut 34. Each long strut 30 is connected to a first short strut 32 at apeak 22 and to a second short strut 34 at a trough 24.

In the various embodiments shown in FIGS. 1-3 each junction 36 defines asingle junction reservoir 12, wherein all of the junction reservoirs 12of a given strut band 20 are substantially circumferentially aligned. Insome embodiments however, a junction defines a plurality, such as 1, 2,3, 4 or more junction reservoirs.

In some embodiments, the connectors 40 comprise a first arm 42 whichextends from a junction 36 on one strut band 20 and a second arm 46which extends from a junction 36 on an adjacent strut band 20. At leasta portion of the first arm 42 comprises a first U-shaped link 44 and atleast a portion of the second arm 46 comprises a second U-shaped link48. Each first U-shaped link 44 opens in a first direction and eachsecond U-shaped link 48 opens in a second direction substantiallyopposite the first direction. Though the specific orientation of theopening of the links can be varied and in any direction, in theembodiments shown in FIG. 1-3, each link 44 and 48 opens in asubstantially circumferential direction or substantially perpendicularto a longitudinal axis of the stent 10.

At least a portion of the first U-shaped link 44 and at least a portionof the second U-shaped link 48 have a shared portion 50. The sharedportion 50 of each connector 40 is disposed between one of the peaks 22on one strut band 20 and a longitudinally adjacent trough 24 of anadjacent strut band 20. In embodiments where the stent 10 includes aplurality of connectors 40 between adjacent strut bands 20, the sharedportions 50 between any two strut bands 20 are substantiallycircumferentially aligned.

If desired the strut bands 20 or a single continuous can be angledrelative to a longitudinal axis of the stent to provide the band(s) witha helical or helical-like configuration. In such an embodiment theshared portions 50 of connectors 40 between a given pair of strut bands40 can likewise be slanted or angled relative to the longitudinal axis.

In the embodiment depicted in FIG. 2 each long strut 30 defines at leastone strut reservoir 14. In some embodiments, one or more of the longstruts 30 define a plurality of strut reservoirs 14. The number of strutreservoirs 14 on a given long strut 30 can be varied from one to abouttwelve, depending on the length of the long strut 30. In someembodiments the number of strut reservoirs 14 is between at least threeto nine. In the embodiment depicted in FIG. 2, in each long strut 30 oneof the strut reservoirs 14 is in substantial circumferential alignmentwith the junction reservoirs 12 of a given strut band 20. Where there isa plurality of strut reservoirs 14 on a long strut 30, preferably theadditional reservoirs 14 are spaced equidistantly from one another andare distributed evenly on either side of the central reservoir incircumferential alignment with the junction reservoirs 12.

The various components of a stent (struts, connectors, reservoirs, etc.)can have a variety of physical characteristics, such as length, width,thickness, etc, of which each can also be varied. In the embodimentsdepicted in FIG. 2 however, each long strut 30 has a long strut width,31 and each first and second short strut 32/34 has a short strut width33. The long strut width 31 is greater than the short strut width 33.Alternatively, in the embodiment shown in FIGS. 1 & 3 long strut width31 is substantially the same as the short strut width 33.

In some embodiments, such as those shown in FIGS. 1 and 2, each arm 42and 46 of the connectors 40 have an arm width 45. The arm width is lessthan either the long strut width 31 or the short strut width 33. In atleast one embodiment, such as is depicted in FIG. 3, the width 45 of thearms 42 and 46 can vary along their lengths, particularly if thepresence of connector reservoirs 16 necessitate a greater width region47 in order to accommodate the desired cross-sectional area of thereservoirs 16.

In some embodiments, such as for example those depicted in FIGS. 1-2 theshared portion 50 of each connector 40 defines a single connectorreservoir 16. As can be seen in the illustrations, the cross-sectionalarea 51 of a given connector reservoir 16 is greater than thecross-sectional area 53 of junction reservoir 12 or the cross-sectionalarea 55 of a strut reservoir 14 (areas 51, 53, and 55 are depictedshaded).

In some embodiments such as in the stent 10 depicted in FIG. 3, at leasta portion of the first U-shaped link 44, adjacent to the shared portion50, defines at least one connector reservoir 16 and at least a portionof the second U-shaped link 48, adjacent to the shared portion 50,defines at least one connector reservoir 16. In the embodiment shown,the area 51 of each connector reservoir is less than or substantiallyequal to the area 53 of each junction reservoir 12.

In the embodiment depicted in FIG. 3 the first U-shaped link 44 and thesecond U-shaped link 48 each define a plurality of first connectorreservoirs 16 a. A region of the first arm 42 adjacent the firstU-shaped link 44 and a region of the second arm 46 adjacent the secondU-shaped link 48 each define a second plurality of connector reservoirs16 b. The first plurality 16 a is greater than the second plurality 16b.

The particular configuration and arrangement of the connector reservoirs16 is not limited to only those configurations/patterns shown in FIGS.1-3. The distribution, size, shape and configuration of the connectorreservoirs (as well as the junction reservoirs and strut reservoirs) canbe modified, in order to provide desired distribution/elutioncharacteristics of one or more drugs or other therapeutic agents.

A therapeutic agent may be a drug or other pharmaceutical product suchas non-genetic agents, genetic agents, cellular material, etc. Someexamples of suitable non-genetic therapeutic agents include but are notlimited to: anti-thrombogenic agents such as heparin, heparinderivatives, vascular cell growth promoters, growth factor inhibitors,Paclitaxel, etc. Where an agent includes a genetic therapeutic agent,such a genetic agent may include but is not limited to: DNA, RNA andtheir respective derivatives and/or components; hedgehog proteins, etc.Where a therapeutic agent includes cellular material, the cellularmaterial may include but is not limited to: cells of human origin and/ornon-human origin as well as their respective components and/orderivatives thereof. Where the therapeutic agent includes a polymeragent, the polymer agent may be apolystyrene-polyisobutylene-polystyrene triblock copolymer (SIBS),polyethylene oxide, silicone rubber and/or any other suitable substrate.

The stent 10 shown and described herein may be made from any suitablebiocompatible materials including one or more polymers, one or moremetals or combinations of polymer(s) and metal(s). Examples of suitablematerials include biodegradable materials that are also biocompatible.By biodegradable is meant that a material will undergo breakdown ordecomposition into harmless compounds as part of a normal biologicalprocess. Suitable biodegradable materials include polylactic acid,polyglycolic acid (PGA), collagen or other connective proteins ornatural materials, polycaprolactone, hylauric acid, adhesive proteins,co-polymers of these materials as well as composites and combinationsthereof and combinations of other biodegradable polymers. Other polymersthat may be used include polyester and polycarbonate copolymers.Examples of suitable metals include, but are not limited to, stainlesssteel, titanium, tantalum, platinum, tungsten, gold and alloys of any ofthe above-mentioned metals. Examples of suitable alloys include, but arenot limited to: platinum-iridium alloys, cobalt-chromium alloys,including Elgiloy and Phynox, MP35N alloy and nickel-titanium alloys,for example, Nitinol.

The stent 10 may be made of shape memory materials such as superelasticNitinol or spring steel, or may be made of materials which areplastically deformable. In the case of shape memory materials, the stentmay be provided with a memorized shape and then deformed to a reduceddiameter shape. The stent 10 may restore itself to its memorized shapeupon being heated to a transition temperature and having any restraintsremoved therefrom.

The stent 10 may be manufactures by methods including cutting or etchinga design from a tubular stock, from a flat sheet which is cut or etchedand which is subsequently rolled or from one or more interwoven wires orbraids. Any other suitable technique which is known in the art or whichis subsequently developed may also be used to manufacture the stent 10disclosed herein.

In some embodiments the stent 10, or its delivery system, may includeone or more areas, bands, coatings, members, etc. that is (are)detectable by imaging modalities such as X-Ray, MRI, ultrasound, etc. Insome embodiments at least a portion of the stent is at least partiallyradiopaque.

The above disclosure is intended to be illustrative and not exhaustive.This description will suggest many variations and alternatives to one ofordinary skill in this art. The various elements shown in the individualfigures and described above may be combined or modified for combinationas desired. All these alternatives and variations are intended to beincluded within the scope of the claims where the term “comprising”means “including, but not limited to”.

Further, the particular features presented in the dependent claims canbe combined with each other in other manners within the scope of theinvention such that the invention should be recognized as alsospecifically directed to other embodiments having any other possiblecombination of the features of the dependent claims. For instance, forpurposes of claim publication, any dependent claim which follows shouldbe taken as alternatively written in a multiple dependent form from allprior claims which possess all antecedents referenced in such dependentclaim if such multiple dependent format is an accepted format within thejurisdiction (e.g. each claim depending directly from claim 1 should bealternatively taken as depending from all previous claims). Injurisdictions where multiple dependent claim formats are restricted, thefollowing dependent claims should each be also taken as alternativelywritten in each singly dependent claim format which creates a dependencyfrom a prior antecedent-possessing claim other than the specific claimlisted in such dependent claim below.

This completes the description of the invention. Those skilled in theart may recognize other equivalents to the specific embodiment describedherein which equivalents are intended to be encompassed by the claimsattached hereto.

1. A stent comprising: a plurality of strut bands, each strut bandforming a closed path of alternating peaks and troughs, wherein strutbands adjacent one another are connected by a plurality of connectors,each strut band comprising a plurality of long struts, a plurality ofshort struts, and a plurality of junctions, each junction beingpositioned between and connecting a first short strut and a second shortstrut, each long strut being connected to a first short strut at a peakand each long strut being connected to a second short strut at a trough,each junction defining only a single junction reservoir, all of thejunction reservoirs of a strut band being circumferentially aligned,each connector comprising a first arm which extends from a junction onone strut band, and a second arm which extends from a junction on anadjacent strut band, at least a portion of the first arm comprising afirst U-shaped link and at least a portion of the second arm comprisinga second U-shaped link, each first U-shaped link opening in a firstdirection and each second U-shaped link opening in a second directionsubstantially opposite the first direction, at least a portion of thefirst U-shaped link and at least a portion of the second U-shaped linkhaving a shared portion, the shared portion disposed between one of thepeaks on one strut band and a longitudinally adjacent trough of anadjacent strut band, wherein the first U-shaped link and the secondU-shaped link each define a first plurality of connector reservoirs, anda region of the first arm adjacent the first U-shaped link and a regionof the second arm adjacent the second U-shaped link each define a secondplurality of connector reservoirs, wherein the first plurality isgreater than the second plurality.
 2. The stent of claim 1 wherein eachconnector reservoir has a connector reservoir area, each junctionreservoir having a junction reservoir area, the connector reservoir areabeing no greater than the junction reservoir area.